And get him to turn over his finances to my caregiver mother? My dad has dementia and goes to the bank and takes out money without my mother's knowledge and she has no idea what he is spending it on or doing with it. She is afraid he will do something financially reckless. We submitted a letter from his neurologist to the bank that said he is not capable of handling financial affairs, but the bank manager stated that is not enough. We would need a court order. They live in New Jersey.
https://www.agingcare.com/articles/elderly-parent-spends-too-much-money-shopaholic-135925.htm
https://www.agingcare.com/articles/how-to-get-guardianship-of-elderly-parents-140693.htm
However, my question is whether your father was previously in the habit of doing whatever he wanted with his money - or did he previously always "run things by" your mother first? If he never consulted her in the past, he surely won't do it now.
Is your mother a joint account holder? If so, she could sign up for online banking and monitor his withdrawals that way.
Is he actually doing reckless spending.....or it is just your mother's fear? If she has proof, then your mother needs to withdraw most of the money out of the account and put it in a new account that your father cannot touch. She will not be able to stop his "reckless spending" since he is probably powerless to control it. It would be easier to just "cut off" some of his funds so he is limited in what he has to spend.